(A) Line constitution
A welded steel pipe manufactured by roll forming a steel strip to shape a pipe and welding its butted seam is already well known. Recently, an electrically seamed steel pipe manufactured by electrically (resistance) welding of a seam is mainly produced.
For one of the roll forming methods in this case, by the way, there is a whole width reduction bending method in which a strip is bent in whole, with gradually reducing its width, so as to make the whole of a pipe round. As to the forming machines belonging to this method, there are known one shown in FIG. 11 and FIG. 12, supplied by Yoda Co. in U.S.A. (disclosed in the official gazette of Japanese Patent Application Laid-open No. 29,896/1970) and another one shown in FIG. 13 to FIG. 15, supplied by Thorans Co. in U.S.A. (the official gazette of Japanese Utility Model Publication No. 28,897/1971). In the figures, the reference numeral 100 represents a pre-forming roll, 102, 104, 106 and 108: break-down rolls, 110 . . . : inner rolls, EF: an edge forming roll, CR: cage rolls, 1F, 2F and 3F: fin pass rolls, and SQ: a squeezing roll, respectively.
However, these machines have such defects as follows:
i) the number of forming rolls is large, PA0 ii) the constraining force to a strip is weak so that the strip is apt to roll. PA0 iii) an applicable range of use for rolls to the change in the size of pipe to be produced is narrow, PA0 iv) the contour of a formed pipe becomes easily a discontinuous polygonal form due to the influence of rolls (See: FIG. 16), and PA0 v) there is large load in the final stage of fin pass forming, because the bending work can not be satisfactorily carried out in the rough and intermediate forming courses, and in practice, it is required to provide at least three stages of fin pass rolls.
In order to overcome these defects, such a forming machine as shown in FIG. 17 and FIG. 18 has first been developed (the official gazette of Japanese Patent Application Laid-open No. 135,428/1986). This machine is composed so that an edge forming roll EF, first to fourth center bending rolls 1CB, 2CB, 3CB and 4CB and a large number of cage rolls CR . . . arranged on both the sides of these center bending rolls, a plurality of fin pass rolls 1F, 2F and 3F, and a squeezing roll SQ, are arranged in order from the upstream side to the downstream side, wherein the edge forming roll EF serves to bend the pipe edge portions of a strip (FIG. 18a), the first to third center bending rolls 1CB, 2CB and 3CB and the cage rolls CR . . . serve to bend the boundaries of the pipe side portions of the strip and the pipe bottom portion thereof (FIGS. 18b, c and d), the fourth center bending roll 4CB and the cage rolls CR . . . serve to bend the pipe bottom portion (FIG. 18e) so that a pipe is U-shaped in cross section (FIG. 18f ), and the fin pass rolls 1F, 2F and 3F serve to further form the pipe under pressure so that the pipe side portions are protruded, and the pipe edge portions, the boundaries between the pipe edge portions and pipe side portions and the boundaries between the pipe side portions and pipe bottom portion are bent and unbent, and a welder serves to weld the resulting seam and the squeezing roll SQ serve to upset bond the said seam.
Also in this case, there are practically such defects as follows:
1 Since the first to fourth center bending rolls 1CB, 2CB, 3CB and 4CB serve to bend only the boundaries between the pipe side portions and pipe bottom portion and the pipe bottom portion and they are therefor arranged at the center of the strip within a range as wide as one-third of its width (FIGS. 18b to d), and since the first to third center bending rolls 1CB, 2CB and 3CB each comprises a twin type split roll, the contact area of these rolls with the strip is small. Even if all the center bending rolls are driven, accordingly, the transmission of feed torque from the rolls to the strip can not be carried out satisfactorily, and as a result, the strip can not be made to progress smoothly.
In order to drive all the center bending rolls, it is necessary to make the machine large-scaled and it is difficult to ensure the space where the cage rolls are to be installed, also leading to the increase of installation expense.
2 Since the second and third center bending rolls 2CB and 3CB each is a twin type split roll (See: FIG. 19 and FIG. 20, wherein FIG. 19 shows a case of a larger size of a pipe to be produced and FIG. 20 shows a case of a smaller one), the formation of dents and roll flaws on the strip, in particular in the split rolls of the down rolls, will be caused by their roll corners.
3 Since the first to fourth center bending rolls 1CB, 2CB 3CB and 4CB each has an independent stand structure, there are required much labor and a long time for the exchange of these rolls.
4 As to the down rolls of the second and third center bending rolls 2CB and 3CB, their roll space must be changed, in spite of the presence of the cage rolls on both the sides thereof, every time the size of a pipe to be produced is changed, and there are, namely, required much labor and a long time for the adjustment of the rolls.
5 Since it is necessary to provide at least three stages of fin pass rolls 1F, 2F and 3F, there are required much labor and a long time for the exchange of these rolls.
Due to consideration of these facts, the present invention is intended to provide a machine for manufacturing welded steel pipes and a method for handling the machine.
Of conventional forming stands for manufacturing electrically seamed steel pipes, these are used several stages of forming stands of the breakdown roll system or center bending roll system, in the rough and intermediate forming processes. These respective stands are independent of one another, and in each of these stands, upper and down rolls are incorporated in a common housing by way of chocks. Accordingly, the exchange of rolls in each forming stand is carried out one by one through the stand side drawing-out system or chock top drawing-out system.
In these roll exchange techniques, however, there are required much labor and a long time in such a case that most rolls must be exchanged, for instance when the size of a pipe to be produced is changed.
The present invention is intended to solve such problems in the prior art, and to improve the rate of operation.
In such a welded pipe forming machine, however, a pipe is curved down by a force applied thereto from cage rolls in the last zone L of a cage roll forming zone, and in the sledding of a strip, its pipe end does not move smoothly into the next first fin pass roll 1F, and it may move out of the pass line so that pipe forming becomes impossible. Even if the pipe end does so move, the contact of the pipe with the down roll of the first fin pass roll 1F may be too strong, leading to the easy formation of roll flaws on the pipe. When a strip is subjected to the width-reduction forming by right and left cage rolls, furthermore, its pipe bottom portion may be deformed, namely folded partly so that the pipe forming result is inferior.
The present invention is intended to eliminate such defects in the prior art, and to achieve the stable forming of pipes.
(B) Edge bending roll
As to a edge bending roll for bending the edges of a steel strip in a forming machine which bends the strip continuously, there is known the technique disclosed in the official gazette of Japanese Patent Application Laid-open No. 167,025/1983 (FIG. 34). According to this technique, an upper roll 36, of the edge bending rolls, is a pair of right and left split rolls 36a and 36b put on one shaft, wherein the pair of these split rolls 36a and 36b are such that the radius of curvature of the split roll surfaces on the mutually opposite face sides thereof, i.e. on the inner surface sides and the radius of curvature of the roll surfaces on the non-opposite face sides thereof, i.e. on the outer surface sides are different. The pair of these split rolls 36a, 36b are made to be changeable for each other in the putting position with respect to a shaft 37 so that both the inner and outer face sides of these split rolls 36a, 36b can be reversed in position. It is, therefore, possible to form strip edges for two sizes of pipes to be produced, by use of the pair of these split upper rolls 36a, 36b together with down rolls 1.
A strip edge forming roll for a welded steel pipe serves to pass a strip while it is held between both the upper and down rolls, thereby forming on the edges of the strip a curved portion corresponding to the size of a pipe to be produced. It is, therefore, necessary to exchange the said rolls, every time the size of a pipe to be produced is changed. Such roll exchange requires much labor in proportion to the sizes of pipes to be produced.
The present invention is intended to provide an edge bending roll for welded steel pipes, in which the above problems are solved.
(C) Split forming roll adjusting device
A roll forming machine in a welded steel pipe manufacturing line for working a steel strip continously comprises upper rolls and down rolls as the forming rolls, in which a steel strip is passed between the rolls so as to be bent in the so-called flower form. If the forming roll is exchanged every time the size of a pipe to be produced is changed, there are required a large number of forming rolls different in size, and their exchange is not easy, leading to increase of cost. Recently, a split roll system has been, therefore, mainly used.
This split roll system is such that the forming roll is composed of split members divided right and left into two parts, i.e. split rolls, wherein the size of a pipe to be produced can be changed by adjusting the space between the split rolls. As to an adjustment means therefor, there are known, for instance one of having a helical adjustment mechanism, disclosed in the official gazette of Japanese Patent Application Laid-open No. 28,627/1982 and another of exchanging a spacer between split rolls, disclosed in the official gazette of Japanese Patent Application Laid-open No. 209,722/1982.
However, the former adjustment means is composed such that the horizontal main shaft thereof is a screw in itself and a pair of nuts screw-engaged with the said screw, wherein a pair of split rolls movably mounted on the main shaft are moved in the axial direction, respectively, by screw-moving the said nuts, so that the space between the split rolls can be adjusted. Accordingly, there is a large possibility of such a risk that the main shaft may be damaged due to the concentration of stress, when any large load is applied to the split rolls. Furthermore, the former adjustment means is not suitable, in particular in the case of manufacturing pipes from a thin sheet, in which high accuracy is required, because it has no backlash adjustment mechanism.
The latter adjustment means is such that a spacer is made to intervene between a pair of right and left split rolls and the said spacer is exchanged with one different in size at need. Every time the spacer is exchanged, accordingly, there are required so much labor and long time, because it is necessary to detach a main shaft from the machine and to detach the split rolls and the spacer from the main shaft, and then to assemble the split rolls and another spacer different in size in place of the old one and incorporate them into the machine.
The present invention is intended to solve such problems in the prior art and to stabilize the quality of the product.
(D) Upper roll actuating apparatus
An upper roll which serves to cause a strip to progress as it is held between the upper roll and a down roll whereby it is gradually shaped into a tubular form, is provided so as to be adjustable in vertical position, in order that the roll surface of the said upper roll is made to accord with a pass line for strips different in thickness and the strips are pressed down. The upper roll actuating apparatus therefor is usually provided so that screw shafts are provided standingly from the chocks at both the ends of an upper roll put-on shaft, and these screw shafts are incorporated in the worm jucks at both the right and left portions of a worm shaft supported on a stand, whereby the upper roll can be moved up and down, with the rotation of the worm shaft in both the normal and reverse directions. The elimination of backlash in this appararus will be carried out by use of a special oil-hydraulic jack provided between the chocks at both the ends of a down roll put-on shaft and the chocks of the upper roll put-on shaft.
As to the elimination of backlash in such a conventional apparatus as mentioned above, there are such defects that it is difficult to carry out the elimination of backlash, because the space between both the upper roll put-on shaft and down roll put-on shaft is narrow, and it is necessary to detach and attach the oil pipings of the said oil-hydraulic jack, when a stand on the movable side is taken off or mounted on these roll put-on shafts, for exchange of the rolls.
The present device is intended to eliminate such defects as mentioned above, and to carry out properly the elimination of backlash.
(E) Cage rolls
In general, for the cage roll forming an electrically seamed steel pipe, there has been hitherto used such a forming machine as shown in FIG. 47 and FIG. 48. This machine is composed so that a plurality of inner rolls 110 . . . , whose roll widths are smaller in order, are arranged from the upstream side to the downstream side, and a large number of outer rolls, i.e. cage rolls CR . . . , CR . . . are arranged on both the sides of the said inner rolls, at heights and directions fitting to the forming situations, wherein a strip fed therein is gradually bent into a U-shaped form, and further into a circular form by applying force to the strip from the inside and the outside by these rolls.
As to the cage rolls CR . . . , CR . . . of the prior art, by the way, there are two types, as shown in FIG. 49 to FIG. 50, one whose roll surface is of a flat face (for example, disclosed in the official gazettes of Japanese Utility Model Publication No. 19,371/1987 and Japanese Patent Application Laid-open No. 174,216/1985) and the other whose roll surface is of a convexly curved face (for example, in the official gazette of Japanese Patent Application Laid-open No. 202,122/1984). Both of them can be applicable to various sizes of pipes to be produced.
In these cage rolls, however, there are such defects of making the roll-contacted portion of a formed steel pipe flat in a stripe-pattern so that its good appearance is strikingly ruined and its commercial value is decreased. In particular, the latter of the two types of cage rolls is excessively defective.
The present invention is intended to eliminate these defects in the prior art.